Disclosed herein are carbon black phase change inks and methods for making same. In one embodiment the carbon black phase change ink composition can comprise (1) a low polarity ink carrier comprising (A) a low polarity wax, and optionally (B) an ester-terminated polyamide, (2) a dispersant, and (3) a carbon black colorant. The ink can be resistant to substantial aggregation and settling of the carbon black colorant in the melt and up to about the jetting temperature of the ink as well as when exposed to freeze thaw cycles. In one embodiment, the phase change ink can be a low energy carbon black phase change ink.
Another embodiment is directed to a method which comprises (a) incorporating into an ink jet printing apparatus the above-described phase change ink composition; (b) melting the ink; (c) causing droplets of the melted ink to be ejected in an image wise pattern onto an intermediate transfer member; and (d) transferring the ink in the image wise pattern from the intermediate transfer member to a final recording substrate.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink j et printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
U.S. Pat. No. 5,783,657, U.S. Pat. No. 5,998,570 and WO 98/17704, (Pavlin et al), the disclosures of each of which are totally incorporated herein by reference, disclose a low molecular weight, ester-terminated polyamide that may be blended with a liquid hydrocarbon to form a transparent composition having gel consistency. The ester-terminated polyamide is prepared by reacting “x” equivalents of dicarboxylic acid wherein at least 50 percent of those equivalents are from polymerized fatty acid, “y” equivalents of diamine such as ethylene diamine, and “z” equivalents of monoalcohol having at least 4 carbon atoms. The stoichiometry of the reaction mixture is such that 0.9≦{x/(y+z)}≦1.1 and 0.1≦{z/(y+z)}≦0.7. The reactants are heated until they reach reaction equilibrium.
U.S. Pat. No. 6,111,055 (Berger, et al), the disclosure of which is totally incorporated herein by reference, discloses an ester terminated dimer acid-based polyamide which is blended with a solvent to form a gel. The solvent may be flammable, and a wick may be added to the resulting gel to form a candle. The said ester terminated dimmer acid-based polyamide is prepared by thermal condensation of a diacid, a diamine and a monoalcohol.
Compositions suitable for use as phase change ink carrier compositions are known and are described in U.S. patent application Ser. No. 10/881,047, the disclosure of which is totally incorporated herein by reference.
U.S. Pat. No. 6,878,198, the disclosure of which is totally incorporated herein by reference, discloses a phase change ink composition comprising (a) an ink carrier comprising a monoamide and a tetra-amide, and (b) oxidized pigment particles, said pigment particles having oxygen-containing functional groups on the surfaces thereof.
U.S. Patent Application 20050113482, the disclosure of which is totally incorporated herein by reference, also discloses a process for preparing a phase change ink composition which comprises (a) a phase change ink carrier, said carrier comprising at least one nonpolar component and at least one polar component, and (b) pigment particles, said process comprising (1) selecting at least one of the polar carrier components to be a pigment particle dispersant; (2) admixing the pigment particles with the dispersant; (3) extruding the mixture of pigment particles and dispersant in an extruder at a temperature that is at or above the peak crystallization temperature of the dispersant and below about the peak melting temperature of the dispersant, thereby forming a pigment dispersion; (4) subsequent to extrusion of the pigment dispersion, adding to the pigment dispersion any remaining polar components and the nonpolar component; and (5) subjecting the resulting mixture of pigment dispersion, polar component, and nonpolar component to high shear mixing to form an ink.
European Patent Application 1535973 A1, the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (a) an ink carrier which comprises a monoamide, a tetra-amide, or a mixture thereof; (b) a polyalkylene succinimide; and (c) pigment particles.
A need remains for improved phase change inks, and in one embodiment, low energy solid inks which permit phase change ink jet printers to perform at more moderate operating conditions, some of which include a lower drum temperature and a reduced pre-heat temperature for substrates, than with conventional phase change inks. For example, a need exists for phase change carbon black inks which can be jetted at a temperature lower than conventional jetting temperature as described below. These carbon black inks can also have excellent robustness. This can be achieved with the use of gellants. There is consequently a need for carbon black ink compositions that enables the use of gellants at lower than conventional operating conditions and ink compositions that do not interfere with the gelling process. While these carbon black inks give excellent print quality and performance at higher energy levels, there is still a need for carbon black inks that minimize penetration of the colorant in the paper during the transfer/fusing stage of the printing process for minimum show-through after fusing at low energy conditions. Furthermore, there is a need for carbon black phase change inks that generate prints with good performance in automatic document feeders. Additionally, there is a need for stable (no settling of pigment) carbon black ink dispersions. Thus, a need exists for a carbon black phase change ink which is resistant to aggregation and settling of the carbon black pigment particles, and more particularly, in a phase change ink jet printer, when the standby-mode printer temperature for the ink is at less than the temperature at which the gel transition for the ink is observed. Moreover, a need remains for carbon black phase change inks that print successfully on paper and transparency stock. The ability to meet the needs described above regarding black phase change inks per se are even more difficult to achieve for carbon black phase change inks because of the problems associated with the handling of carbon black materials.